Typical load control devices are operable to control the amount of power delivered to an electrical load, such as a lighting load or a motor load, from an alternating-current (AC) power source. Wall-mounted load control devices are adapted to be mounted to standard electrical wallboxes. A dimmer switch comprises a controllably conductive device (e.g., a bidirectional semiconductor switch, such as, a triac), which is coupled in series between the power source and the load. The controllably conductive device is controlled to be conductive and non-conductive for portions of a half-cycle of the AC power source to thus control the amount of power delivered to the load (e.g., using a phase-control dimming technique). A “smart” dimmer switch (e.g., a digital dimmer switch) comprises a microprocessor (or similar controller) for controlling the semiconductor switch and a power supply for powering the microprocessor. In addition, the smart dimmer switch may comprise a memory, a communication circuit, and a plurality of light-emitting diodes (LEDs) that are powered by the power supply.
An electronic switch (e.g., a digital switch) comprises a controllably conductive device (e.g., a relay or a bidirectional semiconductor switch), a microprocessor, and a power supply. In contrast to a smart dimmer switch, the controllably conductive device of an electronic switch is not controlled using the phase-controlled dimming technique, but is controlled to be either conductive or non-conductive during a half-cycle of the AC power source to thus toggle the electrical load on and off. Wall-mounted digital sensor dimmers and sensor switches may further comprise occupancy detection circuits, such that the dimmers and switches are able to operate as occupancy sensors to automatically turn on lighting loads in response to the presence of an occupant (i.e., an occupancy condition) and automatically turn off the lighting loads in response to detecting the absence of an occupant (i.e., a vacancy condition).
The power supply and control circuitry of some wall-mounted digital sensor dimmers and sensor switches may be configured to conduct current through an earth ground connection. It is desirable to minimize the amount of current conducted through the earth ground connection. For example, standards may limit the amount of current conducted the earth ground connection to approximately 500 μA or less. This may be difficult in some installations, for example, those that include occupancy detection circuits (e.g., which may be a pyroelectric infrared (PIR) detector and/or an ultrasound detector) that require relatively substantial current for operation.